private void EnqueueToSTPNextWorkItem(WorkItem workItem, bool decrementWorkItemsInStpQueue)
{
lock (_lock)
{
// Got here from OnWorkItemCompletedCallback()
if (decrementWorkItemsInStpQueue)
{
--_workItemsInStpQueue;
if (_workItemsInStpQueue < 0)
{
_workItemsInStpQueue = 0;
}
--_workItemsExecutingInStp;
if (_workItemsExecutingInStp < 0)
{
_workItemsExecutingInStp = 0;
}
}
// If the work item is not null then enqueue it
if (null != workItem)
{
workItem.CanceledWorkItemsGroup = _canceledWorkItemsGroup;
RegisterToWorkItemCompletion(workItem.GetWorkItemResult());
_workItemsQueue.Enqueue(workItem);
//_stp.IncrementWorkItemsCount();
if ((1 == _workItemsQueue.Count) &&
(0 == _workItemsInStpQueue))
{
_stp.RegisterWorkItemsGroup(this);
Trace.WriteLine("WorkItemsGroup " + Name + " is NOT idle");
_isIdleWaitHandle.Reset();
}
}
// If the work items queue of the group is empty than quit
if (0 == _workItemsQueue.Count)
{
if (0 == _workItemsInStpQueue)
{
_stp.UnregisterWorkItemsGroup(this);
Trace.WriteLine("WorkItemsGroup " + Name + " is idle");
_isIdleWaitHandle.Set();
_stp.QueueWorkItem(new WorkItemCallback(this.FireOnIdle));
}
return;
}
if (!_workItemsGroupStartInfo.StartSuspended)
{
if (_workItemsInStpQueue < _concurrency)
{
WorkItem nextWorkItem = _workItemsQueue.Dequeue() as WorkItem;
_stp.Enqueue(nextWorkItem, true);
++_workItemsInStpQueue;
}
}
}
}
/// <summary>
/// Waits for a work item or exits on timeout or cancel
/// </summary>
/// <param name="millisecondsTimeout">Timeout in milliseconds</param>
/// <param name="cancelEvent">Cancel wait handle</param>
/// <returns>Returns true if the resource was granted</returns>
public WorkItem DequeueWorkItem(
int millisecondsTimeout,
WaitHandle cancelEvent)
{
//This method cause the caller to wait for a work item.
//If there is at least one waiting work item then the
//method returns immidiately with true.
//If there are no waiting work items then the caller
//is queued between other waiters for a work item to arrive.
//If a work item didn't come within millisecondsTimeout or
//the user canceled the wait by signaling the cancelEvent
//then the method returns false to indicate that the caller
//didn't get a work item.
WaiterEntry waiterEntry = null;
WorkItem workItem = null;
lock (this)
{
ValidateNotDisposed();
// If there are waiting work items then take one and return.
if (_workItems.Count > 0)
{
workItem = _workItems.Dequeue() as WorkItem;
return(workItem);
}
// No waiting work items ...
else
{
// Get the wait entry for the waiters queue
waiterEntry = GetThreadWaiterEntry();
// Put the waiter with the other waiters
PushWaiter(waiterEntry);
}
}
// Prepare array of wait handle for the WaitHandle.WaitAny()
WaitHandle [] waitHandles = new WaitHandle [] {
waiterEntry.WaitHandle,
cancelEvent
};
// Wait for an available resource, cancel event, or timeout.
// During the wait we are supposes to exit the synchronization
// domain. (Placing true as the third argument of the WaitAny())
// It just doesn't work, I don't know why, so I have lock(this)
// statments insted of one.
int index = WaitHandle.WaitAny(
waitHandles,
millisecondsTimeout,
true);
lock (this)
{
// success is true if it got a work item.
bool success = (0 == index);
// The timeout variable is used only for readability.
// (We treat cancel as timeout)
bool timeout = !success;
// On timeout update the waiterEntry that it is timed out
if (timeout)
{
// The Timeout() fails if the waiter has already been signaled
timeout = waiterEntry.Timeout();
// On timeout remove the waiter from the queue.
// Note that the complexity is O(1).
if (timeout)
{
RemoveWaiter(waiterEntry, false);
}
// Again readability
success = !timeout;
}
// On success return the work item
if (success)
{
workItem = waiterEntry.WorkItem;
if (null == workItem)
{
workItem = _workItems.Dequeue() as WorkItem;
}
}
}
// On failure return null.
return(workItem);
}
